The present invention relates to a coupler for use with light conducting system fibers of a fiber optical system to couple-out and couple-in light to the system fibers, wherein the coupler has at least three coupler fibers such as optical glass fibers for connection to the system fibers and the coupler fibers are positioned on a support to lie in a plane with two of the coupling fibers extending in side by side coupling relationship with end faces being flush with at least the third coupler fiber with its end face abutting against the end faces of the first and second fibers so that the light in the pair of fibers is coupled into the third fiber and the light entering the coupler in the third fiber can be coupled into the pair of fibers.
Input/output coupling elements which utilize at least three fibers are known and described in the copending U.S. patent application Ser. No. 068,218, filed Aug. 20, 1979 which issued on Apr. 20, 1982 as U.S. Pat. No. 4,325,604 and based on German application P 28 42 276.6. These types of coupling elements or couplers are simple to manufacture and always had low insertion losses for the light signals. Therefore, they are particularly suited for use in optical communications particularly in data buses in which, due to a great distance between subscribers and/or the number of subscribers that are included in the information exchange or network, high path attenuations occur. For use in optical communication systems, glass fibers of the coupler or coupling elements are connected to the system fibers of the optical communication systems.